Power amplifiers are found in a variety of industrial, commercial, and consumer electronic products. For example, power amplifiers are utilized in mobile phones, laptops, wireless router, audio applications that drive loudspeakers, in radio frequency (RF) circuits, including the RF circuits found in mobile phones, and in computer equipment. Typically, the power amplifier is found operating between a source device and a destination device that form part of an electronic product. Often, a source device does not provide signals at a high enough signal level for use by a destination device. Thus, power amplifiers may be provided between source devices and destination devices so that signals from the source device can be amplified and received by the destination device at the appropriate signal levels.
Power amplifiers are sensitive to environmental conditions, particularly moisture, and thus need to be protected to maintain them working efficiently. Protective films are often provided to cover the power amplifier and thereby prevent moisture and other contaminants from causing damage. Unfortunately, current deposition techniques, such as sputtering deposition processes and chemical vapor deposition (CVD) processes, are not capable of depositing the protective material that forms the film in a substantially uniform manner. For instance, sections on the surface of the power amplifier and other related circuitry may have high aspect ratios and create shadowed areas that do not receive as much protective material during sputtering deposition processes or the CVD processes. These shadowed areas may leave voids and pin-holes in the protective film that expose the power amplifier to moisture and other environmental conditions. The moisture that enters through these pin-holes and voids can interfere with the operation of the power amplifier, damage the electronic components in the power amplifier, and can eventually render the power amplifier inoperable.
The high currents experienced by power amplifiers makes them particularly vulnerable to the problems caused by moisture relative to other types of electronic devices. These high currents magnify the detrimental effects of moisture penetrating the circuit component. Thus, finding a solution that can adequately deal with the fine contour features associated with the fabrication of a power amplifier during wafer fabrication is particularly important.
Thus, what are needed are better methods of applying a protective coating on a power amplifier that better conforms to the varying surfaces and fine contour features of the power amplifier.